1. Field of the Invention
The present invention relates to a door interlock device for a transformer room of a vacuum circuit breaker, more particularly, to a door interlock device for a transformer room of a vacuum circuit breaker which is structured such that a door of a transformer room is opened by a user only when a ground switch is in a closed state.
2. Description of the Conventional Art
In general, a vacuum circuit breaker is provided in a distribution board for operation or control of a power line system and an operation of a motor in a power plant or a substation, together with other various electric equipment. Further, the vacuum circuit breaker is usually disposed within a cradle which is fixed to the distribution board, in an insertable and drawable manner.
In the distribution board, there are a running (operation) position where a main line and a load terminal of a vacuum circuit breaker are connected to a main line and a load terminal of a cradle to supply a voltage and a current, and a test position where the main line and the load terminal of the vacuum circuit breaker are separated from the main line and the load terminal of the cradle so that an inspection of an operation state of the vacuum circuit breaker can be performed. When the circuit breaker is in the running position, the circuit breaker is operated in case of a fault current such as a short circuit and a ground fault to prevent an incidental accident. On the other hand, when the circuit breaker is in the test position where the circuit is not operated, it is indispensible to provide an additional ground switch at a rear side of the distribution board in order to secure human and physical safety.
Meanwhile, at a lower portion of the cradle, a power transformer is disposed within an instrumental power transformer room. Similarly to the circuit breaker, the power transformer also has a running position where the power transform is performed by being connected to the load terminal, and a test position for maintenance and repair.
When the power transformer is damaged or a power fuse is broken by a trouble which is generated in the running procedure so that maintenance and repair is required, a user can be protected from danger in a case where the maintenance and repairing is performed in a ground state of the circuit breaker. That is, when a user unintentionally opens the door of the transformer room for maintenance and repair, the user may be exposed to danger such as a high voltage, thereby resulting in an accident.
FIGS. 1 and 2 illustrate a switch box in accordance with the conventional art, in which FIG. 1 is a perspective view illustrating a switch box in accordance with the conventional art, and FIG. 2 is a perspective view illustrating the switch box of FIG. 1 in which a ground switch is closed in a state where electric equipment in a distribution board has been excluded.
The structure and operation of the switch box in accordance with the conventional art will be described with reference to FIGS. 1 and 2.
The switch box 1 may be divided into an upper part and a lower part. In the upper part of the switch box 1, a circuit breaker room 6 (CB Room) in which a circuit breaker 2 is accommodated, is provided and at the rear part thereof, a ground switch 3 is disposed. At the lower part of the switch box 1, there is provided a power transformer room 7 (PT Room) which is opened and closed by a power transformer room door 5 and a PT truck 4 is accommodated therein. A power transformer 8 is accommodated in the power transformer room 7 in a disposed state on the PT truck 4, and a power fuse 9 may be disposed at the upper portion of the power transformer 8.
As shown in FIG. 2, it can be noted that the door 5 may be opened in a state where the ground switch 3 is closed.
In a case where repairing work is required when the power fuse 9 is broken due to a fault current, the repairing work is performed by drawing out the PT truck 4 after opening the door 5.
According to the conventional art, as shown in FIG. 2, the transformer room door 5 may be opened irrespective of the closing or opening position of the ground switch 3. Thus, even though the circuit breaker 2 is moved to a test position due to a fault current, a residual voltage may remain at the power transformer room 7 and the load terminal. Accordingly, it is necessary to perform the maintenance and repairing work after removing the residual voltage by closing the ground switch 3 to secure safety of a user and equipment. However, when the power transformer room door 5 is opened in a case where the ground switch 3 is not closed, there may be a serious problem in that a user may be placed into a dangerous situation due to the residual voltage remaining within the power transformer room 7.